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Old 17th February 2009, 11:48 AM   #11
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Join Date: Dec 2007

Quote:
Originally posted by Vlauga
Hi, milen007!

In any case, at DC supply of filament of tubes to associate ~ +25V it is possible to any wire of a feed of filament (only for one!)

BW, VU
hi Vlauga

mind elaborate the point above?

nope, its 6t4. no need direct heating. i know i make my own life harder.

reason i try dc is that my locally custom PT for my preamp is of low quality. no problem with voltage on B+. but when it come to filament supply. while drawing only 2A it drop to 5.6VAC. which i think is no good. as my preamp got hum... it sounds like the mobile phone that near the speaker but constant and its audible at almost 2 feet away. i hope that this dc with correct voltage would cure this.

off the shelf trafo is nowhere i can find that supply 6.3v. with dc supply by using off the shelf PT, say 30ct or less, i can manage to get the desired voltage which is 6.2vdc and i have this dc psu laying around.. the one with lm317..

secondly i would like to know if dc supply give better sound. i am in the leaning stage as this is my first diy tube preamp.


any suggestions really appreciated.

another question.

so how could that capacitor of only 4.7uF on the regulated dc psu can cause the PT to operate hot? as i saw schematic from lm317 datasheet has capacitors on psu output?

any link that i can read more about this? thx in adv


erwin
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Old 17th February 2009, 04:00 PM   #12
Vlauga is offline Vlauga  Russian Federation
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In case of hot PT at you two alternatives of a problem.

1. The discarded transformer. Disconnect it from current of users. Switch it on in AC. If through hour work he remains cold, it is necessary go to the second point.

2. Total quantity of a consumed current filaments of tubes of your amplifier. Compare to passport value of current of the secondary winding of the transformer (1.2A). The first value should be less or equally second.

Inform, what from these points there is a true?

In any case, иcпользование such transformer in similar requirements it is intolerable. Under certain conditions it can fail with critical effect.

BW, VU

P.S. Yes. The main thing to tell has forgotten!
Under your scheme. It is necessary for you to expel R drop and the capacitor 4.7u in case you use an AC for filament supply.
Rdrop it is necessary for you only in case the secondary winding voltage above (on 5 %) 6.3 V at the connected filaments of tubes.
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Old 17th February 2009, 04:38 PM   #13
Vlauga is offline Vlauga  Russian Federation
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Yes... Hammond 166K6 (115V/60Hz) - Indonesia AC 50Hz/220V = ?

Your solution?
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Old 17th February 2009, 06:16 PM   #14
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It appears the posted PS schematic one of Poindexter's; you could ask him why the caps are there, as I am kind of wondering myself.

I am also just finishing a breadboard for his music machine and that schematic also shows a 4.7u across the filament secondaries and a .01 across the transformer secondaries. I would guess it's for noise suppression but I'm no expert.

If your filament voltage is too low, you certainly do not need the Rdrop.
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Old 18th February 2009, 12:58 AM   #15
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Quote:
Originally posted by Vlauga
In case of hot PT at you two alternatives of a problem.

1. The discarded transformer. Disconnect it from current of users. Switch it on in AC. If through hour work he remains cold, it is necessary go to the second point.

2. Total quantity of a consumed current filaments of tubes of your amplifier. Compare to passport value of current of the secondary winding of the transformer (1.2A). The first value should be less or equally second.

Inform, what from these points there is a true?

In any case, 8c?>;L7>20=85 such transformer in similar requirements it is intolerable. Under certain conditions it can fail with critical effect.

BW, VU

P.S. Yes. The main thing to tell has forgotten!
Under your scheme. It is necessary for you to expel R drop and the capacitor 4.7u in case you use an AC for filament supply.
Rdrop it is necessary for you only in case the secondary winding voltage above (on 5 %) 6.3 V at the connected filaments of tubes.
hi Vlauga

i have use this psu that rated 3A to power ta2024(if i am not mistaken draw 400mA idle or normal working and 3A peak) and they are working nicely. just a tad of warm. can be consider not even warm only few degree above room temperature.

the PT is rated 3A as well. which worse case would be able to deliver 2A. its quite big and heavy.

"In any case, 8c?>;L7>20=85 such transformer in similar requirements it is intolerable. Under certain conditions it can fail with critical effect." what does this mean?

i do not use Rdrop when i ac powering. only the cap of 4.7uF. and they drop to 5.6VAC when load around 2A (tube rectifier and 4 pcs 6t4 filament).

when i try this regulated psu thats rated for 3A. i only try it on the 4pcs 6t4 filaments. which i estimated 1A or max 1.2A. hence its confusing that the PT and the 2n3055 are very hot and untouchable.

Quote:
Originally posted by Vlauga
Yes... Hammond 166K6 (115V/60Hz) - Indonesia AC 50Hz/220V = ?

Your solution?
i do not use hammond 166K6. i custom wound locally my PT to get the right secondary voltage. yep. indonesia ac 50Hz/220v.

Quote:
Originally posted by boywonder

It appears the posted PS schematic one of Poindexter's; you could ask him why the caps are there, as I am kind of wondering myself.

I am also just finishing a breadboard for his music machine and that schematic also shows a 4.7u across the filament secondaries and a .01 across the transformer secondaries. I would guess it's for noise suppression but I'm no expert.

If your filament voltage is too low, you certainly do not need the Rdrop.
hi boywonder
yes its Poindexter's psu schematic for 6t4. i take part of it as i do not know how to draw schematic.

if i am not mistaken he said the 4.7uF is to improve the heater supply but you better confirm with him bout this. i saw few schematic with caps on secondary AC as well but forget the value.

my filament voltage is too low. hence i do not use the Rdrop at all.

0.01uf on secondary is kinda snubber network and many people use it. its discuss in threat below discussing the right value for certain VA PT.
Tuning a PS Transformer on a GainClone.
help!!! why the PT is hot.

will try the recommended lm317 i got in my drawer and report back.

Erwin
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Old 18th February 2009, 03:01 AM   #16
Vlauga is offline Vlauga  Russian Federation
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Your case very simple!
I have told already about two points.
Thus you have not given any concrete information.... The scheme and used details...
As to you in this case to help...?
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Old 19th February 2009, 12:43 PM   #17
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this is the psu schem i use to power the heater 1A. the 2n3055 is getting very hot and the power transfomer become very hot to touch.

TR1=BC177
TR2=BD140
TR3=2n3055
IC=LM723

i float this with 26K and 121k resistor from B+ to the ground of this psu output.

PT is 18v CT 18v and rated 3A.

however, i connect this output to the 4.7uF capacitor from the schematic above. but without the Rdrop resistor.

ps: just quotes the custom transformer for just the heater supply cost 2 or 3 times more from this psu with off the rack PT

TIA

erwin
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Old 21st February 2009, 07:42 AM   #18
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anyone opinion? TIA

Erwin
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